A first family of solutions is known from the prior art in which the link between the control shaft of the blanking member of the valve, and the actuator, is made via levers making it possible to create a thermal insulation by the distance between the valve subjected to very high temperatures, and the actuator whose temperature must remain moderate. These solutions present many drawbacks. They involve the use of numerous mechanical parts to ensure the transmission. These parts are subjected to high temperatures, leading to expansions that are difficult to control. They are also reflected by accelerated wear, resulting from the radial loads exerted on the transmission elements. The application EP2044354 presents an exemplary embodiment.
A second family of solutions provides a direct mechanical link between the blanking member and the output shaft of the actuator, and cooling means making it possible to keep the temperature of the actuator in conditions compatible with the constraints of the electronic and electromechanical components. By contrast, these solutions avoid the drawbacks stated for the first family of solutions.
The solutions of the prior art, in particular those providing a direct mechanical link between the blanking member and the actuator, present a drawback linked to the discrepancy constraints on both mechanical and thermal levels. On this account, the patent application WO2012038351 describes a butterfly valve driven by a gear motor.
To ensure a satisfactory mechanical coupling, making it possible to transmit the rotation torque without play, and reliably, an axis common to the actuator and to the blanking member is used, or two axes aligned and fitted together, for example coupled by a rigid link, for example splined shafts, are used. The consequence is a high thermal transmission, and the transfer of the heat from the valve to the actuator. To compensate for this effect, it has been sought in the prior art to cool a part of the actuator, for example by a cooling circuit.
Many prior art solutions aim to increase the transmission of heat coming from the valve to cooled areas of the actuator, which make it possible to discharge the heat. These solutions lead to unsatisfactory compromises: in effect, the valve is designed to operate at high nominal temperatures, and the thermal link with cooled areas is of little interest, inasmuch as the fluid circulates at its nominal temperature. They also lead to high thermal gradients, in a relatively small space, between the hot fluid and the cooling circuit.
In order to reconcile an effective mechanical link with a thermal insulation, a valve has been proposed in the prior art, described in U.S. patent Publication No. application US 2008017816. This patent describes an exhaust valve comprises a valve body, a valve supported by a shaft inside the valve body, and an actuator which drives the shaft to displace the valve relative to the valve body.
U.S. Pat. No. 8,480,054 describes another known solution for coupling a torsionally and thermally insulating rigid shaft, with multiple degrees of freedom to allow misalignment. The coupling device makes it possible to reduce the transfer of heat and isolation from vibrations between the actuator and the valve. The coupling device generally comprises a coupling shaft coupled in rotation at its opposing ends to the input and output shafts by torsion spring mechanisms. The torsion spring mechanisms comprise stirrups blocking rotation of the shaft coupling the input and output shafts. The torsion spring mechanisms allow a limited range of axial displacement and of pivoting between the coupling shaft and the input and output shafts and are preloaded to avoid the valve rotation hysteresis.
U.S. Pat. No. 6,598,619 also describes a valve which comprises a closure element, a motive force device, a coupling element, and a spacing element. The body defines a flow passage which is arranged along a longitudinal axis. The closure element is arranged in the flow passage and comprises a first shaft which is prolonged along a first axis which is oblique relative to the longitudinal axis. The closure element can rotate on the first axis between a first position which substantially prevents the flow through the flow passage and a second position which generally allows flow through the flow passage.
The motor rotates the closure element between the first position and the second position, and comprises a second shaft which can rotate on a second axis. The coupling element linking the first and second shafts to transmit the rotation from the device to the closure element. The coupling element is elastic relative to the first and second shafts. The spacing element isolates the device relative to the wall, and generally defines a volume which contains the coupling element.
Also known is PCT patent Publication No. WO2013/021133 describing a dosing device comprising a valve body provided with a check valve adapted to be displaced between a closure position and an opening position, and a transmission axis having a first end linked to the check valve and a second end linked to a cam element, a rotary electrical actuator comprising a stator assembly and a rotor assembly that rotates about a rotation axis. The rotor assembly comprises a magnetic yoke bearing a rotor magnet and also a roller fixed onto the magnetic yoke off-center relative to the rotation axis and movable in the cam element so as to transform the rotary movement of the rotor assembly into a movement of the transmission axis. Also known is the German patent application DE10344218 or EO1431638 describing other solutions of the prior art.
The drawbacks of these known solutions is that the thermal transmission is indeed reduced at the level of the axes, but remain through the links between the body of the actuator and the body of the valve. These two parts are linked by bolts and by adjacent surfaces ensuring a thermal coupling.
If, on the contrary, the valve and the actuator are separated, the problem is that of the bulk of the assembly. To allow a good integration in a vehicle, it is necessary for the valve to be compact and not to have two distinct parts separated from one another. A person skilled in the art is therefore faced with a dilemma: addressing the thermal constraint means separating the valve in which the hot gases circulate from the electromagnetic actuator. But, addressing the compactness constraint means, on the contrary, bringing these two parts together.